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User Guide 616
Configuring ARP Overview
1
Overview
ARP (Address Resolution Protocol) is used to map IP addresses to MAC addresses. Taking
an IP address as input, ARP learns the associated MAC address, and stores the IP-MAC
address association in an ARP entry for rapid retrieval.
1.1 Supported Features
ARP Table
The ARP table displays all the ARP entries, including dynamic entries and static entries.
Dynamic Entry: Automatically learned and will be deleted after aging time.
Static Entry: Added manually and will be remained unless modified or deleted manually.
Static ARP
You can manually add ARP entries by specifying the IP addresses and MAC addresses.
Gratuitous ARP
Gratuitous ARP is a special kind of ARP. Both the source and destination addresses of the
gratuitous ARP packet are the sender its own IP address. It is used to detect duplicate IP
address. If an interface sends a gratuitous ARP packet and no replies are received, then the
sender knows its IP address is not used by other devices.
Proxy ARP
Normally, the ARP packets can only be transmitted in one broadcast domain, which means
if two devices in the same network segment are connected to different Layer 3 interfaces,
they cannot communicate with each other because they cannot learn each other’s MAC
address using ARP packets.
Proxy ARP solves this problem. As shown below, when a host sends an ARP request
to another device that is not in the same broadcast domain but on the same network
segment, the Layer 3 interface with Proxy ARP enabled will respond the ARP request with
its own MAC address if the destination IP is reachable. After that, the ARP request sender
sends packets to the switch, and the switch forwards the packets to the intended device.
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